ILLUMINATING THE OCEANS 



at one end. Pyrosoma (a creature of tropical seas) is 

 responsible for some extraordinary displays of phos- 

 phorescence. Each creature in the floating colony has two 

 small patches of light-producing cells at the base of a 

 tube, which when stimulated discharges light. At the 

 point of irritation the individuals begin emitting light 

 and (as if the remaining members of the colony were 

 responding to the signal) the light spreads until all the 

 individuals are giving forth light, so that the whole colony 

 is ablaze. 



Land creatures which emit light are beyond the 

 scope of this book — numbers of them are of course 

 well known. But the luminous land creatures form light- 

 giving groups which are not comparable, in numbers or 

 in the efficiency of their devices, with the inhabitants of the 

 sea which are able to emit floods, patches and flashes of 

 hght. 



Numbers of theories have been propounded in 

 attempts to explain the working of the mechanisms — if we 

 can call them mechanisms — which produce the light 

 emitted by sea creatures. 



Among earlier explanations was Mayer's theory that 

 the light from the sun is absorbed and given forth again 

 by the organic protoplasm — a theory which contributed 

 nothing. Brugnatelli advanced the hypothesis that the 

 food of the light-giving animal contains light energy 

 before being swallowed, and that, after digestion, 

 specialized organs convert the energy into light — but he 

 had no explanation of the functioning of the light organs. 

 Macaire enlarged upon the presence of phosphorous and 

 coagulated albumen. Spallanzi wrote about the oxygen 

 producing slow combustion within the creatures, but his 

 ideas comprised no kind of explanation. 



So theories were adumbrated, modified and discarded, 

 until Todd and McCartney advanced the theory that 

 has been developed and generally accepted since — that 

 animal luminosity is solely dependent upon the vital 



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